The present invention relates generally to carburetors for internal combustion engines and, more particularly, to an improvement in float arms of the type utilizing bimetallic construction for varying the level of fuel in the float chamber in accordance with changes in the ambient temperature to change the air-fuel ratio to comply with engine demand.
Generally, it is known that the air-fuel mixture provided by a carburetor becomes richer as the ambient temperature is increased. In order to compensate for this undesired enrichment of the air-fuel mixture, it has been proposed and it is known to adjust the level of fuel in the float chamber of the carburetor in accordance with the change in the ambient air temperature. A float monitors the fuel level in the float chamber and is operatively connected to the float valve by a float arm so that adjustments in the fuel level will correspondingly adjust the air-fuel mixture.
In the past, it has been attempted to form the float arm to incorporate a bimetallic construction. Two examples of such prior constructions are illustrated in FIGS. 1 and 2. Such prior float arms which incorporate a bimetallic construction, however, have not been put into practical use for several reasons.
Thus, it has not been possible to obtain a sufficiently large variation of the fuel level in the float chamber with the known constructions of the float arm. More particularly, in order to obtain a sufficiently large variation of the fuel level in the float chamber, it has been necessary to reduce the thickness of the bimetallic arm which inconveniently but necessarily reduces the rigidity of the float arm to an impractically low level.
For instance, in the case of the prior art construction shown in FIG. 1, the float arm 1 is constituted by a bimetallic construction, i.e., of two strips of different metals or alloys fused to each other. However, as noted above, it is necessary to reduce the relative thickness of the bimetal portion in order to obtain a large effective deflection of the bimetal by providing a large effective length of the bimetal portion. As a consequence, the rigidity of the arm is reduced to such an extent that the arm is unusable. In addition, a lateral pressure is exerted on the float valve by the deviation of the float arm which hinders the correct operation of the float valve.
In the prior art construction shown in FIG. 2, only the float-valve actuating portion la of the float arm is formed of a bimetallic construction. Such construction, however, can provide only a small displacement of the float valve, so that it is necessary to again reduce the relative thickness of the bimetal, resulting in an impractically reduced rigidity of the arm as a whole.